The invention relates to a gear unit for the drive of a rotation tube.
Drive solutions for rotating tubes, such as tube mills or rotary kilns, are characterized along the drive trains thereof by the characteristic configuration beginning with a motor, a coupling, a step-down or speed reducing teeth gear unit, and the thereto coupled tube mill. The gear unit converts the torque of the drive source, which is most typically configured as an electric motor, and, additionally, modulates the output via setting of the speed transmission ratio to that required to achieve the desired output rate of rotation, which is often dictated by the material to be milled by the tube mill.
DE 27 23 319 A1 discloses a two-step multi-path cylindrical gear transmission via which, by means of an inner power distribution, a central drive for tube mills, material size reducers, and similar rotating tubes is created. The distribution of power makes possible an increase of the transferable power output with limited space usage. The power transfer is effected exclusively by hardened outer teeth. The motor-side driving pinion and the intermediate shafts are supported at multiple locations by bearings, whereby this arrangement is associated with an increased production-and installation-effort. This central drive is characterized by the multiplicity of necessary individual measures needed to compensate for the errors caused by production and gear tooth factors.
DE 34 18 543 C1 describes a two-way gear transmission with a distribution of power, by which the distribution of power is effected by an axially freely adjustable shaft on which is mounted oppositely disposed inclined tooth helical pinions. The combined application of the power outputs onto a helical gear having an outer tooth set is effected by the interposition of additional intermediate stages. For the operation of the gear unit of this type, the upper limit of the transferable power outputs is reached at approximately 3000 kW. Higher power outputs can only be achieved with an enlargement of the diameter of the take-off stage. However, with regard to this possibility, which can on principle be considered, it has not been taken into account that the production technical restrictions and the therewith-associated economic arguments work against this approach.
DE 35 34 940 C2 describes an alternative concept that builds upon the principle of power output branching for the drive of tube mills. In this arrangement, the drive stage is a planetary gear and the take-off stage is a cylindrical gear unit. An outer teeth set on the tube mill replaces the gear of the take-off stage of the two-way gear unit disclosed in DE 34 18 543 C1. By reason of the opening of the housing, a requirement in implementing this concept, there is, as a result of the raw environmental influences and the therewith associated wear of the drive components, an increased need for maintenance efforts and efforts to keep the unit ready for operation.
DE 28 41 330 B2 discloses a planetary gear unit with an output branching to two planetary paths with a common planet carrier. The planetary gear unit combines, at the take-off, the previously segregated output streams. The co-axially guided sun shafts are supported at pre-determined locations via roller bearings in the gear unit housing. The other components of the drive chain, hollow gears, planetary gears, and planet carriers are, in any event, supported on bearings at pre-determined locations or, respectively, fixedly mounted relative to the housing. A relative rotation of the sun shafts to one another is not provided. By reason of this guidance of the shafts, in order to compensate for radial and torque disturbances, special configuration measures must be undertaken to compensate for such loads. The torque loading compensation is effected by means of an input-side power distributing coupling.
In operations in the upper output region, planetary gear units are utilized, in connection with which multiple planetary stages are serially performed. Also, it must be taken into account in this connection that the maximum external dimensions considerably increase with an increase of the power output to be transferred. The requirement to produce a pre-determined given transmission ratio from the operational process militates against the deployment of symmetrical coupling linkages.
The invention provides a solution to the challenge of configuring a gear unit of the afore-mentioned type such that the requirements for a low maintenance central drive for rotating tubes such as tube mills or rotary kilns which exhibits a compact configuration, and the requirements for the respective individually required transmission ratio, or speed step-up1 through a simple construction configuration with suitably adapted components, preferably for the upper power output range of more than 3000 kW, can be fulfilled.
The inventive gear unit is characterized by the use of a multiple stage helical gear unit on the input side which effects power distribution and a planetary gear unit on the take-off for load-summing stages, the planetary gear unit being comprised of two planetary stages steps operated in parallel to one another. The gear unit is mounted in a multiple-piece, closed gear unit housing which exhibits a very compact configuration. The planetary stages transmit the mechanical output via a common single piece planet carrier to the working machine. The advantageous configuration of the planet carrier leads, as well, in connection with high power outputs to be transferred, to a compact construction with suitable fitness strength whose production via casting or reforming processes and the thereon following finish machining with simple presentable finish tolerances at a high level of quality is ensured.